The industries, feeding their process lines with continuous rolled materials, are looking for some accumulating device to obtain a continuous operation during downtime caused by the joining of the tail end of an old strip to the leading edge of a new strip. Some devices currently in use, bent the material strip around several horizontal axes, for example as it is disclosed in U.S. Pat. No. 4,086,689 of May 2, 1978. Other devices form spirals around a single vertical or a single horizontal axis. These kinds of device are attractive due to the comparatively small overall dimensions and by the ease of installation into existing plants.
The science on how to keep a moving strip in form of spiral coils to save the storage space has been gradually developed in a number of the U.S. patents. Good part of the said science belongs to the development of devices that can facilitate an uninterrupted motion of moving strip to use this kinematics for continuously working cinematographic apparatus. Among those patents are: U.S. Pat. No. 1,706,296 March 1929 by James; and U.S. Pat. No. 3,722,809 March 1973 by Leisring. The said devices can not be used in the process having a need for regular interruptions in the flow of incoming strip during ends-joining operations.
There is a number of moving strip storage devices keeping the said strip in form of spiral coils, and also providing an uninterrupted flow of outcoming strip during a process having regular interruption at incoming flow; having an internal loop of the stored strip with a flexible linear dimentions which allows to change the amount of length stored inside the said devices. Those devices are described in following units of Art: U.S. Pat. No. 2,318,316 May, 1943 by Lawrence; U.S. Pat. No. 3,310,255 March, 1967 by Sendzimir; U.S. Pat. No. 3,506,210 April, 1970 by La TOUR et al.; U.S. Pat. No. 3,628,742 December, 1971 by Fritzsche; U.S. Pat. No. 3,729,144 April, 1973 by Bijasiewicz et al.; U.S. Pat. No. 3,868,065 February, 1975 by Maruszczak; U.S. Pat. No. 4,092,007 May, 1978 by Weatherby et al.; U.S. Pat. No. 4,497,452 February, 1985 by Sendzimir. The said devices are good as long as they are applied to handle very flexible strip materials like telegraphic tapes, as it was first suggested by Lawrence in U.S. Pat. No. 2,318,316. In case of metal strip, the said devices are less attractive. The moving metal strip usually possess less flexibility than common telegraphic tape, so a permanent intercristal deformation could be developed inside the strip body during the motion along the machine loop due to the fact that the said loop has an opposite curvature regarding the curvature within incoming part of the strip storage space involved. Here a metal strip is bent inside the loop in the opposite direction, what is undesirable. For the device itself a change in direction of curvature of moving strip needs a heavy and a complicated construction capable to cope with great inertia of quickly moving metal strip. For heavy gauge materials the inertia and lack of elasticity may never allow to build the said king of device within some reasonable overall dimentions. The other way to handle a metal strip materials must be searched.
There is a number of devices to keep a quickly moving strip with uninterrupted outcoming flow, while incoming flow may have some interruptions, and also utilizing only one directional curvature within the space of the device involved. Those devices are developed in the following patents: U.S. Pat. No. 617,432 January, 1899 by Casler; U.S. Pat. No. 2,032,336 February, 1936 by Strauss; U.S. Pat. No. 3,258,212 June, 1966 by La TOUR; U.S. Pat. No. 3,341,139 September, 1967 by La TOUR; U.S. Pat. No. 3,860,188 January, 1975 by Bradshaw; U.S. Pat. No. 3,999,718 December, 1976 by Ziemba; U.S. Pat. No. 4,012,004 March, 1977 by Tonellato; U.S. Pat. No. 4,410,121 October, 1983 by Wheeler et al.; U.S. Pat. No. 4,456,189 June, 1984 by Wheeler et al.; U.S. Pat. No. 4,473,193 September, 1984 by Cooper et al.; U.S. Pat. No. 4,529,140 June, 1985 by Cooper. The devices by Casler--U.S. Pat. No. 617,432; Strauss--U.S. Pat. No. 3,258,212 and Tonellato U.S. Pat. No. 4,012,004 are mainly intended to handle some light materials coiled around horizontally oriented axis. They do not provide any parts or assemblies to separate the stored spiral convolutions one from another, so a lot of friction forces must be anticipated between the adjacent material convolutions, especially as soon as heavy gauge material going to be processed by those devices. Those devices can not be considered for future application to process a heavy and/or quickly moving metal strip.
The devices by Wheeler et al--U.S. Pat. Nos. 4,410,121 and 4,456,189; and by Cooper, U.S. Pat. No. 4,529,140 et al are utilising some special parts and assemblies to change the main diameter of stored, however, being moved material strip. All those devices do apply a direct force perpendicular to faces of processed coils that should be maintained by a precise synchronization between the parts involved in a common reciprocating motion perpendicular to the faces of stored coils, and the parts involved to control the speed of coiled spiral within the accumulator. The needed synchronization is hard, if only not impossible, to achieve by affordable technical means.
Five additional devices are shown in U.S. Pat. Nos. 3,258,212; 3,341,139; 3,860,188; 3,999,718; 4,410,121. The first three devices take incoming flow of strip at outermost convolution having the outcoming flow in area of innermost convolution. Two last devices are handling the processed material in an opposite direction.
In the preferred device the processed strip is moved inside the accumulator through a set of vertical rolls in the form of a downward helix. At the bottom, the material is transferred around the inner diameter of the storage section of the machine, then through a sequence of several continuous spirals around the machine's vertical center line--towards outermost diameter of the spiral, and, finally, out to feed a mill process line. During the jointing of strip ends the flow of input material is interrupted, but it is essential to maintain continuous feed of outermost spiral convolution that goes into the mill process line without any interruption. While the strip in the machine input line is held to allow the ends-joining operation, the innermost spiral contracts down the inner vertical rolls to the maximum extent. This contraction lasts as long as the outermost spirals are supplied into the mill process line. Only material strip disruption such as in the feed to join another strip, or a machine breakdown, or a control signal engagement may stop this process; Then, controlled by a special signal, the accumulator is gradually filled in to the capacity, as all available spirals must be expanded to the maximum toward the outermost diameter.
Shrinking and rolling out of the spirals are supported by a set of horizontal radially-elongated rolls having a constant rotating surface speed along the machine diameter. The velocities of the mating surfaces of the spirals, however, are not constant. The poor match of the mating velocities generates abnormal friction leading to a greate consumption of energy, frequent maintenance, an excessive need for replacement parts, poor operation, and damages to the processed material.
Nevertheless, the machines utilizing heavy gauge materials do perform their functions, whereas with light gauge materials they tend to malfunction. Here then, we see the second problem of moving materials along the root of continuous spirals. A proper control of the input and the output material speed is not enough to ensure proper operation, while the speed of material expansion from the inner diameter zone into the outer diameter zone also needs to be controlled. With heavy gauge materials expansion speed may be sufficiently controlled by the elastic deformation forces directed toward the spiral tendency to expand it's curvature line. With light gauge materials the elastic deformation forces must be negligible, if even measurable, so the said forces can not ensure a dependable expansion speed. Thus, irregular waves have been observed along the curvature of light gauge material spirals.
The waves generate conditions which damage the spiral surfaces, that is absolutely unacceptable for coated and plated materials. On the other hand, excessive expansion forces may also cause the same kind of damages, due to lack of clearances between adjacent spirals, what is also unacceptable in these processes.
It is important to notice that the kinematic relationship between mating surfaces of the moving spirals and the supporting rolls should influence the spirals to expand, providing the rolls transfer some torque to the spiral. Otherwise, this relationship should influence the spiral to make waves, especially if the rolls take some rotating torque from them. Depending on the material thickness and the elastic deformation involved, the direction and amount of mechanical influence needed to be transferred from the supporting rolls to the spirals, if any, may vary. The existing coil accumulators do not provide any effectively controlled flexibility in kinemetic relationship between the two mating surfaces under consideration, that means they are suitable only for a small group of materials. As long as the said group of materials is smaller than the group of materials that can go through the strip ends-joining equipment, and then through the mill process line, one should expect such machines to be dismissed from a customer's consideration.
A further weak point of the existing machines concerns operating difficulties in setting up proper timing for all the power driven motors to synchronize the machine modes with the cycles of the adjoining material processing line equipment. It is clear that as long as an operator's attention needs to be engaged in controlling the machine, any benefits from machine utilization are undermined.
It is an objective of the invention disclosed herein to provide an improved machine by reducing all the above listed disadvantages down to an acceptable level; and to generate an increased customer demand for the said machine.